Best in-earphones for £40 budget

I have roughly a £40 budget and I'm looking for a pair of good in-earphones for use mostly with my phone.

I listen mostly to heavy metal and rock and they will get a lot of use at the gym so they need to fairly well made obviously and I'm a big fan of the quality of my audio. I also dislike the over the ear earphones.

So far I've had two pairs of Sennheiser CX 300 II earphones, both pairs suffered from one ear playing music and the other not but other then that I was fairly happy with the earphone. Are there better alternatives for the price?